AYER -- A lightning strike during a quickly passing thunderstorm sparked a three-alarm fire in at 19 Columbia St. Thursday afternoon, leaving two families homeless, officials said. There were no reported injuries.

The fire, which was reported shortly after 5 p.m., left fire damage on the building's third floor and attic, and smoke and water damage to the floors below, Fire Chief Robert Pedrazzi said.

A National Grid crew arrived to shut off power to the building as firefighters were wrapping up their job.

Pedrazzi, who lives a few blocks away, said he was alerted to the fire by his wife, who called him after driving by on Columbia Street on her way home. Firefighters from Devens, Littleton, Lunenburg and Devens helped at the scene.

Additional firefighters from Fitchburg, Groton and Westford helped by staffing Ayer fire stations, Pedrazzi said.

The home's owner is listed as Tracie Clark of Tisbury. It was last assessed at $259,900.

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